P6: gtc-to-vcf (VCF/BCF + indexes), harmonisation, exports (plink, bedgraph, finalreport)

- formats/fasta: plain/BGZF FASTA, .fai/.gzi built identical to htslib, index check, build detection,
  contig aliases, mmap genome cache (IN-060..064)
- formats/bgzf, formats/bcf: pure-Python BGZF, tabix .tbi, BCF 2.2 and CSI (OUT-010, OUT-038, OUT-040)
- harmonize/sites: plus-strand mapping with audit rows, indel resolution from SourceSeq (port of GTCtoVCF,
  Apache-2.0) and left normalisation (OUT-014..021, OUT-030, OUT-042)
- harmonize/combine: OUT-031 genotype combination (ploidy-aware, Infinium I/II signal classes, OUT-037)
- pipeline/vcf: `simurg gtc-to-vcf` (per-sample VCF.gz+tbi, --merge cohort BCF+csi, audit parquet)
- pipeline/export: `simurg export bedgraph|finalreport|plink|locus-summary` (OUT-043, OUT-050..052, OUT-071)
- validation: 36 GSA samples vs gtc2vcf: 23.66 M identical calls, 0 unexplained differences; PLINK identical
  to plink2 on 637,397 variants; bcftools validates VCF/BCF and our indexes answer region queries correctly
- fetch_data.sh p6 (Ensembl GRCh38 with checksum), make_oracle_vcf.sh, validate_p6_vcf.py; K-022/K-023

docs/known_unknowns.md

@@ -4,6 +4,8 @@ Plan §20 lists the open questions; this file records what the implementation ha
 
 | ID | Date | Topic | Finding | Status |
 |---|---|---|---|---|
+| K-023 | 2026-09-28 | P6 options not yet implemented | `--auxiliary-loci` (OUT-035), `--info-fields`/`--extra-format` (OUT-012; GENTRAIN/CLUSTER_SEP would also need the EGT), `--merge-snv-indel` (OUT-021), PLINK 2 `.pgen`. Everything else of CLI-022/CLI-023 works. | open |
+| K-022 | 2026-09-28 | VCF oracles' limits (GSA v4 PGx, GRCh38) | gtc2vcf leaves 144 indel probes unresolved (`REF=I`/`D`) that SimurgArray resolves from `SourceSeq`; both leave 49 indels unresolved. GTCtoVCF (python-2.7 era) runs under Python 3 only with two local patches (pyvcf3 `Format` field; skip instead of crash on 3 CYP2D6 indels whose `SourceSeq` has the dash on the right, `[ALLELE/-]`, which SimurgArray handles), and needs the alt-contig loci filtered when the FASTA has no alts. Neither oracle applies ploidy (males' X/Y/MT hets stay diploid). | documented |
 | K-021 | 2026-09-28 | Control metrics on legacy Omni2.5 IDATs | (1) The Omni2.5 manifest lists two bead addresses per control (e.g. 27630314 and 127630314, two bead-pool versions); only one is on a given chip. Absent addresses were NaN and poisoned the bead mean → 1794/2141 samples falsely flagged on both staining metrics. Absent addresses are now skipped. (2) 1290 samples have Biotin (Bgnd) green = 0 exactly (background-subtracted), so staining green is signal/0; QC-008 now defines that as +Inf (pass) and only 0/0 as NaN (flag). | resolved (spec QC-008 amended) |
 | K-020 | 2026-09-28 | QC report scope (P5b) | Implemented: views A–E, linked selection, thresholds modal (apply/download/upload YAML), chip/plate heatmaps, trend table and Tukey box plots, PCA card, xlsx/csv table, privacy options, `--split-by dataset`. Not yet: client-side xlsx export (CSV only), density mode for > 12 000 points (WebGL scatter is used), `--split-by plate|run`, X/Y median R for the sex card (the summary does not carry them; the card shows the sex check instead), methylation datasets (v2). | open (deviations listed) |
 | K-019 | 2026-09-28 | GSA demo relatedness | The 36-sample GSA v4 PGx demo set contains duplicate/replicate pairs (KING φ ≈ 0.50, concordance ≥ 0.9999) and first-degree relatives (φ ≈ 0.25); without a pedigree they are flagged `duplicate_of:`/`unexpected_relatedness` as designed. Useful as a small relatedness fixture. | documented |